Safety handle and probe for portable surface gauge using radioactive source



March 5, 1968 o. a. AULD ETAL 3,372,280

SAFETY HANDLE AND PROBE FOR PORTABLE SURFACE v GAUGE USING RADIOACTIVESOURCE Original Filed June 25 1963 2 Sheets-Sheet 1 INVENTORS David B.Auld Andrew Lowery Robert F. Penny Attorney March 5, 1968 GAUGE USINGRADIOACTIVE SOURCE Original Filed June 25, 1963 2 Sheets-Sheet 2 t I I Iu m lull I w U v 6 iii! 7 r m J I n l v x i n 8 4 2, 0 x 6 2/ 3 4 9 3 22 m WW 0 m e n m y E m e 0 B F r m w 4% m w V b O o DAR United StatesPatent C 3,372,280 SAFETY HANDLE AND PROBE FOR PORT- ABLE SURFACE GAUGEUSING RADIO- ACTIVE SUURCE David E. Anld, 3123 Childers St, AndrewLowery, 4901 Grinnell Drive, and Robert F. Penny, Rte. 1, Justice Brive,all of Raleigh, N.C. 27 609 Continuation of application Ser. No.290,539, June 25, 1963. This application Jan. 20, 1966, Ser. No. 560,3963 Claims. (Cl. 250-406) ABSTRACT OF THE DISCLOSURE A portableradioactive surface gauge employs a probe rod which mounts a radioactivesource and which is constructed so that it will interlock with thehandle of the gauge only when the probe rod source is in a shieldedabove-surface position. The probe can otherwise be releasably securedfor measuring in various sub-surface, direct transmission, positions.The handle remains useful as a handle when the probe rod, which isremovably mounted in the gauge, is completely removed.

This application is a continuation of application'Ser. No. 290,539,filed June 25, 1963, entitled, Safety Handle for Portable Surface GaugeUsing Radioactive Source, and now abandoned.

Radioactive source material is employed in many new gauge devices whichuse the radioactive material as a means for measuring density, moisture,material composition and the like. Particularly where the gauge is madeas a portable unit and safety practices are loose it becomesincreasingly important to design the gauge in a form which encouragessafe use of the radioactive source and makes difficult or impossible anunsafe use of the source. For example, where a radioactive source isabove ground and is unshielded considerable physical harm may result ifthe human body has a close and prolonged exposure to the source. Thesource can of course be shielded but cannot be shut off as such.

' Commercially available radioactive gauges now include a portable typeof surface density gauge which is placed on the surface of the materialbeing measured and through use of a gamma source detects direct andreflected gamma rays as a measure of its density. Certain of thecommercial forms of surface density gauges employ a gamma source whichremains fixed and properly shielded in the housing of the gauge. Otherdensity gauges and particularly of the type made by the assignee of thisinvention place the source in the end of a probe and when in use theprobe is lowered from a safe shielded position within the gauge housingto a measuring position located at some predetermined level in thematerial and below its surface. With the probe source extended out ofits safe position, it is important in practice that it be brought backto its safe shielded position before the gauge is moved otherwise theoperator is apt to receive a harmful exposure. Even though a gauge ofthis kind is heavy because of the lead shielding, the handle isordinarily not affected by the position of the probe and it is easyenough for the operator to carelessly lift the gauge while the probe isextended out of its shielding and thus harm himself. Atomic EnergyCommission license requirements while stringent have not eliminated theproblem. When the source is stored and is physically absent from thegauge proper there is of course no exposure problem. However, even inthis condition the handle structure should act to support the heavyshielding material because the housing itself is open ended, thickwalled lead cylinder 12 that is suitusually made of a thin sheetmaterial not adapted to carry the heavy weight of the shieldingmaterial.

A principal object of the present invention is to provide a handle for aradioactive probe, portable, surface type gauge which handle isgenerally not useful as a handle unless the probe is in a safe shieldedposition.

Another object is to provide a handle for a radioactive probe, portable,surface type gauge which handle can only be locked into handle positionwhen the probe is in a safe shielded position and when locked insuresthat the probe will remain in a safe position.

Another object is to provide a handle structure for a radioactive probe,portable, surface type gauge having a housing enclosing a substantialmass of heavy shielding material which structure can be locked into andunlocked from a handle forming position and in such position is arrangedto be integrally connected to the shielding material.

Another object is to provide a handle for a radioactive probe, portable,surface type gauge which handle can be locked into a handle formingposition irrespective of the presence of the probe and in such positioncan be secured to the probe shielding material located in the gaugehousing.

Another object is to provide an integral safety handle structure whichcan be easily assembled with a radioactive probe, portable, surface typegauge.

These and other objects of the invention will appear from thedescription and drawings in which like numerals refer to like elementsand referring to a preferred embodiment of the invention.

FIGURE 1 is a side elevation of a radioactive probe, portable, surfacetype density gauge having a handle structure embodying the invention andillustrating the probe extended into a ground bore hole to a measuringposition.

FIGURE 2 is a side elevation similar to FIGURE 1 illustrating the probesource lifted out of the bore hole and positioned in a safe position andthe handle structure in handle forming position.

FIGURE 3 is a side perspective illustrating the handle structure innon-handle forming position and in dotted lines an intermediateposition.

FIGURE 4 is a fragmentary perspective of the handle structure in alocked handle forming position.

FIGURE 5 is an enlarged fragmentary perspective of portions of thehandle structure shown in FIGURE 4, the view being taken from the sameside as FIGURE 4 but from an opposite direction.

FIGURE 6 is an elevation cross section taken longitudinally of the gaugeand illustrating the probe source in a safe shielded position and thehandle structure in handle forming position.

FIGURE 7 is an enlarged fragmentary perspective of a pin employed withthe handle structure.

Referring now to the drawings, a radioactive probe, portable, surfacetype gauge of the type being described is frequently used as a soildensity measuring gauge. The type SC109 and type SC surface densitygauges presently manufactured by the assignee of the present inventionare of the type illustrated in the drawings. The illustrated gaugeincludes a housing having an upper section 10 suitably secured to alower section 11, both sections being preferably formed as lightweight,thin wall, molded plastic sections. Shielding for the probe source whenin its safe, shielded position is provided by a hollow,

ably secured to the bottom wall by screws, glue or other means.Additional protection against direct and reflected gamma rays producedby the probe source particularly when in extended position as in FIGURE1, is provided 3 by a substantially rectangular shaped lead block 13that is also secured to the bottom of the housing.

When the probe is extended into measuring position as illustrated forexample in FIGURE 1, measurement of the gamma count is made by anappropriate photomultiplier or Geiger-Mueller counter tube, not shown.The counter is placed in the tubular receptacle 14 which mounts on thefloor of the housing and has an annular cap 15 through which electricalleads, not shown, from the counting device may be passed. Since theinvention is primarily concerned with the probe and handle structuresand not with the counting circuitry such circuitry is not treated infurther detail.

Cylinder 12 mounts a guide tube 16. The probe mounted in tube 16generally takes the form of a vertically positioned and adjustablecircular rod having a suitable handle 21 at one end with the sourceholder 22 and gamma source 23 being located at the opposite end. Matingmale and female threads as indicated at 24 are provided between thesource holder 22 and the main body of probe 20 in order that source 23may be removed and replaced as desired and which facilitates storage ofprobe 20 in an unshielded state.

Gauges using radioactive materials for measuring density, moisture andmaterial composition are designed around the specific radioactivematerial which is to be used. Cesium 137 may, for example, be used assource 23. It is known in the art that gamma radiation is easilycontained by high density shielding material, such as lead and the like,which easily absorb the radiation produced thereby; and also, that thegamma radiation is easily dissipated over a relatively small distance,the formula being the inverse square ratio. Element 20 as used isstainless steel and although this does not trap the radiationimmediately surrounding the source, over the length of the rod it doestrap a quantity sufficient to render the raidation harmless to the userwhen standing above the device. Element 22 may be made from any highdensity material such as lead and the gamma radiation traveling axiallyand downwardly is dissipated in the material to a level which rendersthe same harmless. When the probe has entered the soil, the materialimmediately surrounding the source is thus not of a quantity to blockall of the radiation emitted thereby. The radiation counter which isinserted in receptacle 14 is thereby adapted to accurately count theradiation emitted from the source.

Probe 2G is guided for vertical movement by a relatively large collar 26which surrounds the probe and is fixedly mounted on the top housing wallon a handle base plate 27 by means of suitable screws such as indicatedat 28. Base plate 27 is in turn secured by screws, bolts or other meansto a pair of back up plates 29, 30, disposed within the upper housingsection 10 opposite, respectively the front and rear ends of base plate27. A bolt 31 passes through collar 26, through base plate 27, throughthe upper housing section 10, through the front back up plate 29 and isthreaded into the lead cylinder 12 as indicated at 32. Thus, when baseplate 27 is lifted the load of lead cylinder 12 as well as that of leadblock 13 is transmitted to the base plate 27. The housing itself isthereby relieved of such load.

Adjustment of the source level is accomplished by a detent arrangementwhich includes a series of relatively shallow grooves 33 of uniformcharacter spaced at regular intervals along the length of probe 20. Thegrooves 33 are adapted to receive a detent ball 34 that is continuallyurged inwards by reason of a spring 35 that is held in place by means ofa set screw 36. The ball 34, the spring 35 and the set screw 36 are allmounted in a radially positioned hole provided in the wall of collar 26and as the probe is manually adjusted up and down the detent ball 34will automatically engage one of the grooves 33 and will hold probe 20in the position corresponding to the groove engaged.

Mounted on top of collar 26 as an integral part thereof is a pin 40. Pin40 has a threaded end which is screwed into a mating threaded hole incollar 26, a conical shaped head 41 and a slotted groove 42, anenlargement of the top, slotted groove, portion of pin 40 being shown inFIGURE 7. The handle proper is formed by the L- shaped handle member 45which is pivotedly secured to the base plate 27 by means of the hinge46. As later explained handle 45 must engage and fixedly position probe20 whenever handle 45 is serving as a handle. Therefore, whenever probe26 is being positioned, handle 45 has to be swung out of the Way andwould generally be moved to the vertical position shown in FIGURE 1 andFIGURE 3. In this last mentioned position, it is important to note thatdue particularly to the weight of the lead cylinder 12 and the leadblock 13, the handle 45 is practically useless as a handle. With thehandle in such position, the operator is at the very least given a sharpreminder that the handle is not properly positioned for lifting of thegauge and particularly the probe.

In contrast, when it is desired to manually move the gauge to a newlocation the probe 20 is positioned to the shielded position asrepresented in FIGURE 2 and FIG- URE 6. At this position a speciallyshaped and relatively large groove 50 provided on probe 20 mates with amatching curved portion 51 provided in the end of handle 45 and the pin49 is arranged to pass through a hole 52 provided in handle 45.Positioning is facilitated by first slightly engaging the probe groove50 and the handle portion 51 with the handle tilted as indicated by thedotted line position 6% and then lowering the probe and handle togetheruntil fully engaged. Once handle portion 51 is solidly engaged withgroove 50, a clip member 53 may be pushed between a pair of guides 54 soas to engage the slotted groove 42 of pin 40 and lock handle 45 tocollar 26. A suitable pin locking means of this kind is marketed underthe name Snapslide Fasteners and is sold by the Dimco-Gray Company, 207E. 6th St., Dayton, Ohio. To insure that handle 45 will not thereafterleave this fixed position and to meet government safety requirements, apadlock 55 is provided Which passes through a hole 56 locatedimmediately behind clip member 53.

Of special interest is the fact that groove 50 is made of a differentcharacter than any of the detent recesses or grooves 33. Therefore, thefree end of handle 45 will only interlock with groove 50 and only whenthe probe source 23 is confined in the shielding cylinder 12.Furthermore, handle 45 can only assume handle forming position whensource 23 is safely shielded and the fastening means 53 is operativeonly when source 23 is in a shielded position. As a furthercharacteristic, the handle 45 is usable as a means to comfortably carrythe heavy weight of cylinder 12 and block 13 only when source 23 isproperly shielded.

While the invention is primarily concerned with a handle structure thatis employed with a radioactive probe, mention is made of the fact thatthe handle 45 can be locked into handle forming position with the probe26 completely absent. That is, when probe 20 is physically absent,handle 45 need only engage and be connected to pin 40 inorder to form ahandle.

Having described the invention, we claim:

1. A cooperative safety handle and probe for a portable, radioactive,surface type gauge adapted to take sub-surface measurements by directtransmission including in combination: a vertically disposed elongatedprobe; a radioactive source secured to the bottom of said probe; ahousing removably mounting said probe and including top and bottom wallsarranged perpendicular to the axis of said probe and having openingstherethrough for passage of said probe; a radioactive shielding blocksecured Within said housing to said bottom wall and having an openingtherethrough aligned with both said wall openings and arranged forpassage of said probe; positioning 5 means mounted on said housing andengaging said probe and enabling said probe to be releasably secured invarious vertical positions whereby said source may be positioned incorresponding sub-surface direct transmission measuring positions; a barmember having one end piva otally secured to said top wall at a positionremoved from said top wall opening and its other end free to swing intoand out of engagement with said probe at a position above said top wallopen ng. the free end of said bar member and the surface of said probehaving mating surface formations capable of being arranged to interlock,the surface formation of said probe being located so that said barmember free end surface formation interlocks therewith only when saidsource is positioned within said block, said bar member beingpositionable horizontally and effective as a handle, whenever said probeis mounted in said housing, only when said formations are in interlock;and locking means efl'ective when said probe is mounted in said housingto simultaneously hold said bar member and probe formations in saidinterlock, said source in a shielded position and said bar membersecured to said housing and in a handle forming position, said lockingmeans furthermore being effective when said probe is dlsmounted fromsaid housing to hold said bar member secured to said housing in the samesaid handle forming osition. I

2. A cooperative safety handle and probe as claimed in claim 1 whereinsaid positioning means includes guide means secured to said top wall andadapted to sli receive and guide said probe, a plurality of vert spaceddetent recesses on said, probe and cooperatir tent means in said guidemeans, said guide means, I'Ct 5 and detent means enabling the saidreleasable sec and positioning of said probe in said Correspondingsurface positions.

3. A cooperative safety handle and probe as cl:

in claim 2 wherein said detent recesses are of an 10 character and saidprobe surface formation is of diti character such that when said probeis mounted ir housing said free end of said bar member can be lockedonly with said probe surface formation am with any of said recessesthereby allowing said sour 15 be positioned in use at said sub-surfacedirect transm measuring positions corresponding to said recessespreventing said bar member being employed as a h except when said sourceis in said block.

20 References Cited UNITED STATES PATENTS 2.226.346 12/1940 Mttssman292-2 2,675,487 4'll954 Schallert et al. 250-l 2,998,527 8/1961 Shevicket al. 250- 3,126,484 3/1964 Mceder et al. 250- ARCHIE R. BORCHELT,Primary Examiner.

